Power control management in uplink (ul) coordinated multipoint (comp) transmission

ABSTRACT

Techniques for performing path loss (PL) compensation in coordinated multipoint (CoMP) systems are provided. A method for wireless communications by a user equipment (UE) is provided. The method generally includes selecting, from a plurality of transmission points involved in uplink (UL) coordinated multipoint (CoMP) operations with the UE, a transmission point to associate with for path loss (PL) compensation, and adjusting power of one or more transmissions based on path loss measured based on the selected transmission point

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

This application claims benefit of U.S. Provisional Patent ApplicationNo. 61/592,427, filed Jan. 30, 2012, which is herein incorporated byreference in its entirety.

BACKGROUND

I. Field

Certain aspects of the disclosure generally relate to wirelesscommunications and, more particularly, to techniques for managing powercontrol in uplink coordinated multipoint (CoMP) transmissions.

II. Background

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless networks may be multiple-access networkscapable of supporting multiple users by sharing the available networkresources. Examples of such multiple-access networks include CodeDivision Multiple Access (CDMA) networks, Time Division Multiple Access(TDMA) networks, Frequency Division Multiple Access (FDMA) networks,Orthogonal FDMA (OFDMA) networks and Single-Carrier FDMA (SC-FDMA)networks.

A wireless communication network may include a number of base stationsthat can support communication for a number of user equipments (UEs). AUE may communicate with a base station via the downlink and uplink. Thedownlink (or forward link) refers to the communication link from thebase station to the UE, and the uplink (or reverse link) refers to thecommunication link from the UE to the base station.

A base station may transmit data and control information on the downlinkto a UE and/or may receive data and control information on the uplinkfrom the UE. On the downlink, a transmission from the base station mayobserve interference due to transmissions from neighbor base stations.On the uplink, a transmission from the UE may cause interference totransmissions from other UEs communicating with the neighbor basestations. The interference may degrade performance on both the downlinkand uplink.

SUMMARY

Certain aspects of the present disclosure provide techniques,corresponding apparatus, and program products, for path losscompensation in a coordinated multipoint (CoMP) system.

Certain aspects provide a method for wireless communications by a userequipment (UE) to compensate for differences in path loss. The methodgenerally includes selecting, from a plurality of transmission pointsinvolved in uplink (UL) coordinated multipoint (CoMP) operations withthe UE, a transmission point to associate with for path loss (PL)compensation and adjusting power of one or more transmissions based onpath loss measured based on the selected transmission point.

Certain aspects provide a method for wireless communications by a basestation (e.g., eNB or other type transmission point) to compensate forpath loss. The method generally includes utilizing a first power controlalgorithm to adjust transmit power of a first contention-based randomaccess channel (RACH) transmitted from a UE and utilizing a second powercontrol algorithm to adjust transmit power of a non contention-basedRACH.

Certain aspects provide a method for wireless communications by a userequipment (UE) to compensate for differences in path loss. The methodgenerally includes utilizing a first power control algorithm to adjusttransmit power of a first contention-based random access channel (RACH)to a base station and utilizing a second power control algorithm toadjust transmit power of a non contention-based RACH.

Certain aspects provide a method for wireless communications by a basestation to compensate for path loss. The method generally includesdetermining mobility of a UE and selecting a power control algorithm foruse in controlling power of transmissions from the UE, based on thedetermined mobility.

Certain aspects provide a method for wireless communications by a userequipment (UE) to compensate for path loss. The method generallyincludes measuring path loss (PL) for a plurality of transmission pointsinvolved in uplink (UL) coordinate multipoint (CoMP) transmissions withthe UE and selecting, based on the PL measurements, one of thetransmission points for applying PL compensation.

Certain aspects provide a method for wireless communications by a basestation to compensate for path loss. The method generally includesmeasuring path loss (PL) between a user equipment (UE) and one or moretransmission points involved in uplink (UL) coordinate multipoint (CoMP)transmissions with the UE and taking action to compensate for themeasured path loss.

Certain aspects provide a method for wireless communications by a userequipment (UE) to compensate for path loss. The method generallyincludes measuring both common reference signals (CRS) and channel stateinformation reference signals (CSI-RS) transmitted from transmissionpoints involved in uplink (UL) CoMP transmissions and performing powercontrol for UL transmissions based on both the CRS and the CSI-RS.

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram conceptually illustrating an example of awireless communications network, in accordance with certain aspects ofthe present disclosure.

FIG. 2 is a block diagram conceptually illustrating an example of aframe structure in a wireless communications network, in accordance withcertain aspects of the present disclosure.

FIG. 2A shows an example format for the uplink in Long Term Evolution(LTE), in accordance with certain aspects of the present disclosure.

FIG. 3 shows a block diagram conceptually illustrating an example of aNode B in communication with a user equipment device (UE) in a wirelesscommunications network, in accordance with certain aspects of thepresent disclosure.

FIG. 4 illustrates an example heterogeneous network (HetNet), inaccordance with certain aspects of the present disclosure.

FIG. 5 illustrates example resource partitioning in a heterogeneousnetwork, in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates example cooperative partitioning of subframes in aheterogeneous network, in accordance with certain aspects of the presentdisclosure.

FIG. 7 illustrates an example scenario of a Coordinated MultiPoint(CoMP) transmission, in accordance with certain aspects of the presentdisclosure.

FIG. 8 illustrates another example scenario of a Coordinated MultiPoint(CoMP) transmission, in accordance with certain aspects of the presentdisclosure.

FIG. 9 illustrates example operations that may be performed by a userequipment (UE), in accordance with aspects of the present disclosure.

FIG. 10 illustrates example operations that may be performed, forexample, by a base station to compensate for path loss, in accordancewith aspects of the present disclosure.

FIG. 11 illustrates example operations that may be performed, forexample, by a UE to compensate for path loss, in accordance with aspectsof the present disclosure.

FIG. 12 illustrates example operations that may be performed, forexample, by a base station to compensate for path loss, in accordancewith aspects of the present disclosure.

FIG. 13 illustrates example operations that may be performed, forexample, by a UE to compensate for path loss, in accordance with aspectsof the present disclosure.

FIG. 14 illustrates example operations that may be performed, forexample, by a base station to compensate for path loss, in accordancewith aspects of the present disclosure.

FIG. 15 illustrates example operations that may be performed, forexample, by a UE to compensate for path loss, in accordance with aspectsof the present disclosure.

DETAILED DESCRIPTION

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS thatuse E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, certain aspects of the techniquesare described below for LTE, and LTE terminology is used in much of thedescription below.

Example Wireless Network

FIG. 1 shows a wireless communication network 100, which may be an LTEnetwork. The wireless network 100 may include a number of evolved NodeBs (eNBs) 110 and other network entities. An eNB may be a station thatcommunicates with user equipment devices (UEs) and may also be referredto as a base station, a Node B, an access point, etc. Each eNB 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to a coverage area of an eNB and/or aneNB subsystem serving this coverage area, depending on the context inwhich the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell,a femto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a Closed Subscriber Group (CSG), UEs for users in the home,etc.). An eNB for a macro cell may be referred to as a macro eNB (i.e.,a macro base station). An eNB for a pico cell may be referred to as apico eNB (i.e., a pico base station). An eNB for a femto cell may bereferred to as a femto eNB (i.e., a femto base station) or a home eNB.In the example shown in FIG. 1, eNBs 110 a, 110 b, and 110 c may bemacro eNBs for macro cells 102 a, 102 b, and 102 c, respectively. eNB110 x may be a pico eNB for a pico cell 102 x. eNBs 110 y and 110 z maybe femto eNBs for femto cells 102 y and 102 z, respectively. An eNB maysupport one or multiple (e.g., three) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., an eNB or a UE) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE or an eNB). A relay station may also be a UE thatrelays transmissions for other UEs. In the example shown in FIG. 1, arelay station 110 r may communicate with eNB 110 a and a UE 120 r inorder to facilitate communication between eNB 110 a and UE 120 r. Arelay station may also be referred to as a relay eNB, a relay, etc.

The wireless network 100 may be a heterogeneous network (HetNet) thatincludes eNBs of different types, e.g., macro eNBs, pico eNBs, femtoeNBs, relays, etc. These different types of eNBs may have differenttransmit power levels, different coverage areas, and different impact oninterference in the wireless network 100. For example, macro eNBs mayhave a high transmit power level (e.g., 20 watts) whereas pico eNBs,femto eNBs, and relays may have a lower transmit power level (e.g., 1watt).

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the eNBs may have similar frametiming, and transmissions from different eNBs may be approximatelyaligned in time. For asynchronous operation, the eNBs may have differentframe timing, and transmissions from different eNBs may not be alignedin time. The techniques described herein may be used for bothsynchronous and asynchronous operation.

A network controller 130 may couple to a set of eNBs and providecoordination and control for these eNBs. The network controller 130 maycommunicate with eNBs 110 via a backhaul. The eNBs 110 may alsocommunicate with one another, e.g., directly or indirectly via wirelessor wireline backhaul.

The UEs 120 may be dispersed throughout the wireless network 100, andeach UE may be stationary or mobile. A UE may also be referred to as aterminal, a mobile station, a subscriber unit, a station, etc. A UE maybe a cellular phone, a personal digital assistant (PDA), a wirelessmodem, a wireless communication device, a handheld device, a laptopcomputer, a cordless phone, a wireless local loop (WLL) station, atablet, etc. A UE may be able to communicate with macro eNBs, pico eNBs,femto eNBs, relays, etc. In FIG. 1, a solid line with double arrowsindicates desired transmissions between a UE and a serving eNB, which isan eNB designated to serve the UE on the downlink and/or uplink. Adashed line with double arrows indicates interfering transmissionsbetween a UE and an eNB. For certain aspects, the UE may comprise an LTERelease 10 UE.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition the system bandwidth into multiple(K) orthogonal subcarriers, which are also commonly referred to astones, bins, etc. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (K) may bedependent on the system bandwidth. For example, K may be equal to 128,256, 512, 1024, or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20megahertz (MHz), respectively. The system bandwidth may also bepartitioned into subbands. For example, a subband may cover 1.08 MHz,and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of1.25, 2.5, 5, 10, or 20 MHz, respectively.

FIG. 2 shows a frame structure used in LTE. The transmission timelinefor the downlink may be partitioned into units of radio frames. Eachradio frame may have a predetermined duration (e.g., 10 milliseconds(ms)) and may be partitioned into 10 subframes with indices of 0 through9. Each subframe may include two slots. Each radio frame may thusinclude 20 slots with indices of 0 through 19. Each slot may include Lsymbol periods, e.g., L=7 symbol periods for a normal cyclic prefix (asshown in FIG. 2) or L=6 symbol periods for an extended cyclic prefix.The 2L symbol periods in each subframe may be assigned indices of 0through 2L−1. The available time frequency resources may be partitionedinto resource blocks. Each resource block may cover N subcarriers (e.g.,12 subcarriers) in one slot.

In LTE, an eNB (e.g., eNB 110) may send a primary synchronization signal(PSS) and a secondary synchronization signal (SSS) for each cell (e.g.,cell 102) in the eNB. The primary and secondary synchronization signalsmay be sent in symbol periods 6 and 5, respectively, in each ofsubframes 0 and 5 of each radio frame with the normal cyclic prefix, asshown in FIG. 2. The synchronization signals may be used by UEs (e.g.,UEs 120) for cell detection and acquisition. The eNB may send a PhysicalBroadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe0. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) inthe first symbol period of each subframe, as shown in FIG. 2. The PCFICHmay convey the number of symbol periods (M) used for control channels,where M may be equal to 1, 2, or 3 and may change from subframe tosubframe. M may also be equal to 4 for a small system bandwidth, e.g.,with less than 10 resource blocks. The eNB may send a Physical HARQIndicator Channel (PHICH) and a Physical Downlink Control Channel(PDCCH) in the first M symbol periods of each subframe (not shown inFIG. 2). The PHICH may carry information to support hybrid automaticrepeat request (HARQ). The PDCCH may carry information on resourceallocation for UEs and control information for downlink channels. TheeNB may send a Physical Downlink Shared Channel (PDSCH) in the remainingsymbol periods of each subframe. The PDSCH may carry data for UEsscheduled for data transmission on the downlink. The various signals andchannels in LTE are described in 3GPP TS 36.211, entitled “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical Channels andModulation,” which is publicly available.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNB. The eNB may send the PCFICH and PHICHacross the entire system bandwidth in each symbol period in which thesechannels are sent. The eNB may send the PDCCH to groups of UEs incertain portions of the system bandwidth. The eNB may send the PDSCH tospecific UEs in specific portions of the system bandwidth. The eNB maysend the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to allUEs, may send the PDCCH in a unicast manner to specific UEs and may alsosend the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element may cover one subcarrier in one symbol period andmay be used to send one modulation symbol, which may be a real orcomplex value. Resource elements not used for a reference signal in eachsymbol period may be arranged into resource element groups (REGs). EachREG may include four resource elements in one symbol period. The PCFICHmay occupy four REGs, which may be spaced approximately equally acrossfrequency, in symbol period 0. The PHICH may occupy three REGs, whichmay be spread across frequency, in one or more configurable symbolperiods. For example, the three REGs for the PHICH may all belong insymbol period 0 or may be spread in symbol periods 0, 1, and 2. ThePDCCH may occupy 9, 18, 32, or 64 REGs, which may be selected from theavailable REGs, in the first M symbol periods. Only certain combinationsof REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for the PDCCH. An eNB may send the PDCCH to the UE in anyof the combinations that the UE will search.

FIG. 2A shows an exemplary format 200A for the uplink in LTE. Theavailable resource blocks for the uplink may be partitioned into a datasection and a control section. The control section may be formed at thetwo edges of the system bandwidth and may have a configurable size. Theresource blocks in the control section may be assigned to UEs fortransmission of control information. The data section may include allresource blocks not included in the control section. The design in FIG.2A results in the data section including contiguous subcarriers, whichmay allow a single UE to be assigned all of the contiguous subcarriersin the data section.

A UE may be assigned resource blocks in the control section to transmitcontrol information to an eNB. The UE may also be assigned resourceblocks in the data section to transmit data to the eNB. The UE maytransmit control information in a Physical Uplink Control Channel(PUCCH) 210 a, 210 b on the assigned resource blocks in the controlsection. The UE may transmit only data or both data and controlinformation in a Physical Uplink Shared Channel (PUSCH) 220 a, 220 b onthe assigned resource blocks in the data section. An uplink transmissionmay span both slots of a subframe and may hop across frequency as shownin FIG. 2A.

A UE may be within the coverage of multiple eNBs. One of these eNBs maybe selected to serve the UE. The serving eNB may be selected based onvarious criteria such as received power, pathloss, signal-to-noise ratio(SNR), etc.

A UE may operate in a dominant interference scenario in which the UE mayobserve high interference from one or more interfering eNBs. A dominantinterference scenario may occur due to restricted association. Forexample, in FIG. 1, UE 120 y may be close to femto eNB 110 y and mayhave high received power for eNB 110 y. However, UE 120 y may not beable to access femto eNB 110 y due to restricted association and maythen connect to macro eNB 110 c with lower received power (as shown inFIG. 1) or to femto eNB 110 z also with lower received power (not shownin FIG. 1). UE 120 y may then observe high interference from femto eNB110 y on the downlink and may also cause high interference to eNB 110 yon the uplink.

A dominant interference scenario may also occur due to range extension,which is a scenario in which a UE connects to an eNB with lower pathlossand lower SNR among all eNBs detected by the UE. For example, in FIG. 1,UE 120 x may detect macro eNB 110 b and pico eNB 110 x and may havelower received power for eNB 110 x than eNB 110 b. Nevertheless, it maybe desirable for UE 120 x to connect to pico eNB 110 x if the pathlossfor eNB 110 x is lower than the pathloss for macro eNB 110 b. This mayresult in less interference to the wireless network for a given datarate for UE 120 x.

In an aspect, communication in a dominant interference scenario may besupported by having different eNBs operate on different frequency bands.A frequency band is a range of frequencies that may be used forcommunication and may be given by (i) a center frequency and a bandwidthor (ii) a lower frequency and an upper frequency. A frequency band mayalso be referred to as a band, a frequency channel, etc. The frequencybands for different eNBs may be selected such that a UE can communicatewith a weaker eNB in a dominant interference scenario while allowing astrong eNB to communicate with its UEs. An eNB may be classified as a“weak” eNB or a “strong” eNB based on the received power of signals fromthe eNB received at a UE (and not based on the transmit power level ofthe eNB).

FIG. 3 is a block diagram of a design of a base station or an eNB 110and a UE 120, which may be one of the base stations/eNBs and one of theUEs in FIG. 1. For a restricted association scenario, the eNB 110 may bemacro eNB 110 c in FIG. 1, and the UE 120 may be UE 120 y. The eNB 110may also be a base station of some other type. The eNB 110 may beequipped with T antennas 334 a through 334 t, and the UE 120 may beequipped with R antennas 352 a through 352 r, where in general T≧1 andR≧1.

At the eNB 110, a transmit processor 320 may receive data from a datasource 312 and control information from a controller/processor 340. Thecontrol information may be for the PBCH, PCFICH, PHICH, PDCCH, etc. Thedata may be for the PDSCH, etc. The transmit processor 320 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The transmit processor320 may also generate reference symbols, e.g., for the PSS, SSS, andcell-specific reference signal. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 330 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols, if applicable, and may provide T output symbolstreams to T modulators (MODs) 332 a through 332 t. Each modulator 332may process a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator 332 may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a downlink signal. T downlink signals frommodulators 332 a through 332 t may be transmitted via T antennas 334 athrough 334 t, respectively.

At the UE 120, antennas 352 a through 352 r may receive the downlinksignals from the eNB 110 and may provide received signals todemodulators (DEMODs) 354 a through 354 r, respectively. Eachdemodulator 354 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 354 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 356 may obtainreceived symbols from all R demodulators 354 a through 354 r, performMIMO detection on the received symbols, if applicable, and providedetected symbols. A receive processor 358 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 120 to a data sink 360, and provide decoded control informationto a controller/processor 380.

On the uplink, at the UE 120, a transmit processor 364 may receive andprocess data (e.g., for the PUSCH) from a data source 362 and controlinformation (e.g., for the PUCCH) from the controller/processor 380. Thetransmit processor 364 may also generate reference symbols for areference signal. The symbols from transmit processor 364 may beprecoded by a TX MIMO processor 366 if applicable, further processed bymodulators 354 a through 354 r (e.g., for SC-FDM, etc.), and transmittedto the eNB 110. At the eNB 110, the uplink signals from the UE 120 maybe received by the antennas 334, processed by the demodulators 332,detected by a MIMO detector 336 if applicable, and further processed bya receive processor 338 to obtain decoded data and control informationsent by the UE 120. The receive processor 338 may provide the decodeddata to a data sink 339 and the decoded control information to thecontroller/processor 340.

The controllers/processors 340 and 380 may direct the operation at theeNB 110 and the UE 120, respectively. The controller/processor 340,receive processor 338, and/or other processors and modules at the eNB110 may perform or direct operations 800 in FIG. 8 and/or otherprocesses for the techniques described herein. The memories 342 and 382may store data and program codes for the eNB 110 and the UE 120,respectively. A scheduler 344 may schedule UEs for data transmission onthe downlink and/or uplink.

Example Resource Partitioning

According to certain aspects of the present disclosure, when a networksupports enhanced inter-cell interference coordination (eICIC), the basestations may negotiate with each other to coordinate resources in orderto reduce or eliminate interference by the interfering cell giving uppart of its resources. In accordance with this interferencecoordination, a UE may be able to access a serving cell even with severeinterference by using resources yielded by the interfering cell.

For example, a femto cell with a closed access mode (i.e., in which onlya member femto UE can access the cell) in the coverage area of an openmacro cell may be able to create a “coverage hole” (in the femto cell'scoverage area) for a macro cell by yielding resources and effectivelyremoving interference. By negotiating for a femto cell to yieldresources, the macro UE under the femto cell coverage area may still beable to access the UE's serving macro cell using these yieldedresources.

In a radio access system using OFDM, such as Evolved UniversalTerrestrial Radio Access Network (E-UTRAN), the yielded resources may betime based, frequency based, or a combination of both. When thecoordinated resource partitioning is time based, the interfering cellmay simply not use some of the subframes in the time domain. When thecoordinated resource partitioning is frequency based, the interferingcell may yield subcarriers in the frequency domain. With a combinationof both frequency and time, the interfering cell may yield frequency andtime resources.

FIG. 4 illustrates an example scenario where eICIC may allow a macro UE120 y supporting eICIC (e.g., a Rel-10 macro UE as shown in FIG. 4) toaccess the macro cell 110 c even when the macro UE 120 y is experiencingsevere interference from the femto cell y, as illustrated by the solidradio link 402. A legacy macro UE 120 u (e.g., a Rel-8 macro UE as shownin FIG. 4) may not be able to access the macro cell 110 c under severeinterference from the femto cell 110 y, as illustrated by the brokenradio link 404. A femto UE 120 v (e.g., a Rel-8 femto UE as shown inFIG. 4) may access the femto cell 110 y without any interferenceproblems from the macro cell 110 c.

According to certain aspects, networks may support eICIC, where theremay be different sets of partitioning information. A first of these setsmay be referred to as Semi-static Resource Partitioning Information(SRPI). A second of these sets may be referred to as Adaptive ResourcePartitioning Information (ARPI). As the name implies, SRPI typicallydoes not change frequently, and SRPI may be sent to a UE so that the UEcan use the resource partitioning information for the UE's ownoperations.

As an example, the resource partitioning may be implemented with 8 msperiodicity (8 subframes) or 40 ms periodicity (40 subframes). Accordingto certain aspects, it may be assumed that frequency division duplexing(FDD) may also be applied such that frequency resources may also bepartitioned. For communications via the downlink (e.g., from a cell nodeB to a UE), a partitioning pattern may be mapped to a known subframe(e.g., a first subframe of each radio frame that has a system framenumber (SFN) value that is a multiple of an integer N, such as 4). Sucha mapping may be applied in order to determine resource partitioninginformation (RPI) for a specific subframe. As an example, a subframethat is subject to coordinated resource partitioning (e.g., yielded byan interfering cell) for the downlink may be identified by an index:

Index_(SRPI) _(DL) =(SFN*10+subframe number)mod 8

For the uplink, the SRPI mapping may be shifted, for example, by 4 ms.Thus, an example for the uplink may be:

Index_(SRPI) _(—) _(UL)=(SFN*10+subframe number+4)mod 8

SRPI may use the following three values for each entry:

-   -   U (Use): this value indicates the subframe has been cleaned up        from the dominant interference to be used by this cell (i.e.,        the main interfering cells do not use this subframe);    -   N (No Use): this value indicates the subframe shall not be used;        and    -   X (Unknown): this value indicates the subframe is not statically        partitioned. Details of resource usage negotiation between base        stations are not known to the UE.

Another possible set of parameters for SRPI may be the following:

-   -   U (Use): this value indicates the subframe has been cleaned up        from the dominant interference to be used by this cell (i.e.,        the main interfering cells do not use this subframe);    -   N (No Use): this value indicates the subframe shall not be used;    -   X (Unknown): this value indicates the subframe is not statically        partitioned (and details of resource usage negotiation between        base stations are not known to the UE); and    -   C (Common): this value may indicate all cells may use this        subframe without resource partitioning. This subframe may be        subject to interference, so that the base station may choose to        use this subframe only for a UE that is not experiencing severe        interference.

The serving cell's SRPI may be broadcasted over the air. In E-UTRAN, theSRPI of the serving cell may be sent in a master information block(MIB), or one of the system information blocks (SIBs). A predefined SRPImay be defined based on the characteristics of cells, e.g. macro cell,pico cell (with open access), and femto cell (with closed access). Insuch a case, encoding of SRPI in the system overhead message may resultin more efficient broadcasting over the air.

The base station may also broadcast the neighbor cell's SRPI in one ofthe SIBs. For this, SRPI may be sent with its corresponding range ofphysical cell identities (PCIs).

ARPI may represent further resource partitioning information with thedetailed information for the ‘X’ subframes in SRPI. As noted above,detailed information for the ‘X’ subframes is typically only known tothe base stations, and a UE does not know it.

FIGS. 5 and 6 illustrate examples of SRPI assignment in the scenariowith macro and femto cells. A U, N, X, or C subframe is a subframecorresponding to a U, N, X, or C SRPI assignment.

Uplink CoMP—Power Control Management

In current CoMP deployment scenarios, e.g., Scenario-3 or Scenario-4,there is a pathloss (PL) mismatch between the downlink (DL) serving celland uplink (UL) serving cell. In cases where the UL and DL serving cellsare mismatched, open loop power control (OLPC) based on PL compensationis wrong. A variety of scenarios may be considered in which PLcompensation may be performed in different manners, Scenario-3 andScenario-4 are described below.

In some scenarios, decoupling of control and data (e.g., with datatransmitted from one transmission point and control transmitted fromanother transmission point) may be of relative importance with respectto HetNet CoMP. One such scenario is referred to as CoMP “Scenario-3” inwhich transmission points have different cell-IDs (i.e., control anddata transmissions are decoupled). In this case, a UE may receivecontrol information from a transmission point that is different from thetransmission point of data. For example, control information may bereceived on, for example, legacy PDCCH from a macro-cell and data may bereceived from Remote Radio Heads (RRHs).

FIG. 7 illustrates an example scenario of a Coordinated MultiPoint(CoMP) transmission, in accordance with certain aspects of the presentdisclosure. As seen in FIG. 7, in the UL the UE1 is closest to RRH4. Itmay, therefore, be desirable that UE1 is served by RRH 4 on the uplink.As seen in FIG. 7, UE1 may receive DL TM9 data from RRH4 and mayreceived DL control from eNB1. In this case, UE1 measures the PL on theDL from eNB1 and applies transmit power to RRH4.

However, there may be a PL mismatch between the paths from the eNB1 toUE1 and the UE1 to RRH4.

A second scenario is referred to as CoMP “Scenario-4” in whichtransmission points share the same cell-ID. Consequently, controlinformation transmitted via the PDCCH is common to all points in theCoMP cluster.

As seen in FIG. 8, DL signal is transmitted from one macro cell (i.e.,eNB1) and four picocells (i.e., RRH1, RRH2, RRH3, and RRH4), but theuplink (UL) transmission may use only RRH4, since RRH 4 is closest tothe UE1. This conserves power on UE1.

However, there is a PL mismatch between DL PL measurement and ULapplication. On the DL, the PL is calculated as an aggregate weighted bythe transmission power. On the UL, the PL is dependent on one or morenodes. Reference signal (RS) power definition may be required whentransmitted from all cells.

Some possible solutions are detailed below as approaches 1 a, 1 b and 2.These solutions may be applicable when the UE is stationary and/ormoving with reduced speed. However, when the UE is mobile (i.e., movingwith relatively higher speed), approaches 1 a, 1 b and 2 may exhibitdifferent drawbacks.

A first approach involves RRC-based solutions—without use of channelstate information reference signaling (CSI-RS). In some embodiments,transmit power may be adjusted for random access channel (RACH)transmissions. RACH power is determined based on full open loop PLcompensation and PREAMBLE_RECEIVED_TARGET_POWER. Since the PLmeasurement is inaccurate, PREAMBLE_RECEIVED_TARGET_POWER may be reducedfor all the users within the cell and then power may be ramped up asneeded for transmission.

In determining RACH power it is desirable to use low power for initialRACH transmissions in order to avoid interference to other cells. On theother hand, starting with a very low power delays the RACH procedure.

In some embodiments, for Scenario 3, the desired range of RACH power maybe derived based on the eNB power difference in the HetNet as well ascell RE bias. The UE may associate with the eNB based on the followingequations:

P _(m) −PL _(m) >P _(p) −PL _(p)+bias

which may be re-written as:

PL _(m) <PL _(p)+(P _(m) −P _(p)−bias)

PL mismatch reduces with the increase of Cell Range Expansion (CRE)bias. Initial RACH power may be set according to power differencebetween the nodes and bias values for CRE. For eNB power 46 dB and RRHpower 30 dB scenarios, a bias of 0 dB, 6 dB, 9 dB, and 12 dB may have aworst PL error of a 16 dB, 10 dB, 7 dB, and 4 dB, respectively.

Advantages to this approach may include minimal changes in thespecification. A potential drawback may be possible delay for users,since this is approach relates to a cell configuration.

In some embodiments, Message 3 transmission power may be adjusted.Herein, a bit length used to indicate transmit power control (TPC)commands may be increased for better range. Current TPC commands forMessage 3 utilize 3 bits in the 20-bit UL grant. If RACH is in the rightpower range, for example, −6 dB to 8 dB, then this length should beenough for Message 3 power setting. Alternatively, if RACH is sent athigh power to reduce delay, TPC command bits may be increased forMessage 3.

Techniques may also be used to adjust transmit power for subsequent ULtransmissions (i.e., after RACH and Message 3 transmissions), based onthe Message 3 transmission power. If Message 3 is on target, othertransmissions can be adjusted based on Message 3. Approach 1 a relies onclosed loop power control adjustment. Approach 1 b relies on UE specificPL adjustment, PL delta or P0.

In some embodiments, for approach 1 a, in contention based RACH, lowtransmission power is transmitted initially. This approach relies on aslow start because the PL difference is unknown. For non-contentionbased RACH, for example, when there is a loss of UL synchronization andPL and the base station the UE is communicating with is known, the slowstart may be avoided and delay may be avoided. This provides support forlarger power control step size in the case of large PL difference.

In some embodiments, a new power control (PC) command can be added toenhanced-PDCCH (EPDCCH) design if no PDCCH change desired.

In some embodiments, for approach 1 a, eNB reception-based adaptationmay be used to turn off OLPC. The eNB may have knowledge of which nodeis receiving the UL signal. The eNB may be configured to control when toturn off or turn on OLPC. For high mobility UEs, OLPC may be turned off.For low mobility UEs with correct DL association, OLPC kept on. For lowmobility UE with different DL and UL associations, both theaforementioned options work well. eNB may rely completely on closed loopadjustment or use both open loop and closed loop together.

A second approach involves CSI-RS based solutions. Herein, wheneverthere is a PL mismatch, a different CSI-RS is provided. For example,referring back to FIG. 7, in Scenario-3 CoMP, a CSI-RS may be providedfrom RRH4 to UE1. The CSI-RS may be designed to compensate for PLmismatch.

In some embodiments, each of the RRHs transmits on its own CSI-RS portto allow PL measurements. The PL measurement may be correct from the ULserving cell perspective and the same PL algorithm may be reused withthe PL compensation.

In some embodiments, signaling of specific CSI-RS ports for PLmeasurement may be provided to the UE. The RS power may also be UEspecific. However, the CSI-RS may need to be configured prior toutilization. Also, CSI-RS signaling overhead may be included when UEmobility is high. For example, when the UE passes through many cells, itmay be required to signal many different CSI-RS configurations as the UEgoes from cell to cell.

Enhancements for the CRS-based approach are provided. In someembodiments, for Scenario-3, autonomous OLPC may be based on CRSinterference cancellation (CRS-IC). For advanced UEs with IC, the UE maydetect low power nodes at large bias. The eNB may signal UE the sets ofUL CoMP nodes with corresponding CRS configurations and power settings.The UE may autonomously apply the PL compensation to the cell with thesmallest PL. The UE knows the pico-cell that is closest to it based onthe CSI-RS received by the UE. The UE may receive CSI-RS from differentcells. From the eNB, the UE receives the CSI-RS transmit power.Subtracting the received power from the transmitted power, the UE cancalculate the PL. The UE associates with the cell having the smallest PLfor the UL transmission and applies the OLPC based on that cell.

In some embodiments, the UE may auto adjust the PL compensation based onits knowledge of the nearest eNB. This approach requires minimumsignaling overhead, i.e., eNB signaling to the UE existence of nearbyeNBs and the power settings of the nearby eNBs.

Other Enhancements for CRS Based Approach are also provided. In someembodiments, eNB-based power shaping and partial PL compensation may beused. One drawback of approach 1 a is that it does not have implicitpower-shaping. Implicit power shaping is achieved by eNB-basedpower-shaping algorithms. In a first step of one algorithm, the eNBcalculates PL based on the received signal power, the UE's maximumtransmit power, and the UE's power headroom report. In a second set ofthe algorithm, the eNB transmits a power control command to adjust theUE's transmit power, in order to effectively achieve partial PLcompensation based rate shaping.

In some embodiments, an eNB-based direct interference management schememay be used. Instead of relying on power/rate shaping, eNBs in the ULCoMP set may directly adjust the power of UEs that are causinginterference to a desired level, thus, directly controlling inter-cellinterference.

Other Enhancements for CSI-RS are also possible. One drawback of aCRS-based approach is the requirement for signaling of CSI-RS ports whenthe UE is mobile. In some embodiments, a list of CSI-RS ports and UEautonomous selection of CSI-RS ports based on PL measurements may bedefined. The eNB may signal the list of CSI-RS ports for the UE to modelalong with the transmission power for each of the CSI-RS ports. Forexample, the eNB may send the UE the complete list of ports and the UEmay then performs measurements of these ports in order to identify thePL to each of the nodes. The UE may autonomously apply PL compensationbased on the smallest PL measured from the list of CSI-RS ports and mayassume that the nodes with the smallest PL will be the UL receptionpoints.

In some embodiments, the eNB may be required to signal the UE disjointCSI-RS ports specified for DL CoMP measurements and UL CoMP measurementsin the event that DL and UL may have different CoMP sets.

Enhancements for a Joint Approach based on both CSI-RS and CRS are alsopossible. In some embodiments, the UE may autonomously switch the OLPCbased on CSI-RS and CRS. The CRS is used to measure PL. AdditionalCSI-RS ports may be signaled to the UE only to switch the OLPC on oroff. Alternatively, in some embodiments, CSI-RS may be utilized todecide which PL, measured from CRS, is to be used in power control.

In some embodiments, CRS-IC switching based on CSI-RS detection may beused. For scenario 3, UE uses CSI-RS to discover cell in the event onlyCRS-IC is supported by UE, but does use a Primary Synchronization Signal(PSS) or Secondary Synchronization Signal (SSS) IC. Once the UEdiscovers the cell from CSI-RS, the UE turns on CRS-IC.

In some embodiments, the CSI-RS may be used for PL delta measurement.The CSI-RS-based measurement is performed with a reduced dynamic rangefor PL delta, for example, 0-16 dB, and all other values are pruned out.

FIG. 9 illustrates example operations 900 that may be performed, forexample, by a user equipment (UE) to compensate for differences in pathloss. The operations 900 begin, at 902, by selecting, from a pluralityof transmission points involved in uplink (UL) coordinated multipoint(CoMP) operations with the UE, a transmission point to associate withfor path loss (PL) compensation. At 904, the UE adjusts power of one ormore transmissions based on path loss measured based on the selectedtransmission point.

FIG. 10 illustrates example operations 1000 that may be performed, forexample, by a base station (e.g., eNB or other type transmission point)to compensate for path loss. The operations 1000 begin, at 1002, byutilizing a first power control algorithm to adjust transmit power of afirst contention-based random access channel (RACH) transmitted from aUE. At 1004, the base station utilizes a second power control algorithmto adjust transmit power of a non contention-based RACH.

FIG. 11 illustrates example operations 1100 that may be performed, forexample, by a UE to compensate for path loss. The operations 1100 begin,at 1102, by utilizing a first power control algorithm to adjust transmitpower of a first contention-based random access channel (RACH). At 1104,the UE utilizes a second power control algorithm to adjust transmitpower of a non contention-based RACH.

FIG. 12 illustrates example operations 1200 that may be performed, forexample, by a base station to compensate for path loss. The operations1200 begin, at 1202, by determining mobility of a UE. At 1204, the basestation selects a power control algorithm for use in controlling powerof transmissions from the UE, based on the determined mobility.

FIG. 13 illustrates example operations 1300 that may be performed, forexample, by a UE to compensate for path loss. The operations 1300 begin,at 1302, by measuring path loss (PL) for a plurality of transmissionpoints involved in uplink (UL) coordinate multipoint (CoMP)transmissions with the UE. At 1304, the UE selects, based on the PLmeasurements, one of the transmission points for applying PLcompensation.

FIG. 14 illustrates example operations 1400 that may be performed, forexample, by a base station to compensate for path loss. The operations1400 begin, at 1402, by measuring path loss (PL) between a userequipment (UE) and one or more transmission points involved in uplink(UL) coordinate multipoint (CoMP) transmissions with the UE. At 1404,the base station takes action to compensate for the measured path loss.

FIG. 15 illustrates example operations 1500 that may be performed, forexample, by a UE to compensate for path loss. The operations 1500 begin,at 1502, by measuring both common reference signals (CRS) and channelstate information reference signals (CSI-RS) transmitted fromtransmission points involved in uplink (UL) CoMP transmissions. At 1504,the UE performs power control for UL transmissions based on both the CRSand the CSI-RS.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and/or write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal Generally, where there are operations illustrated inFigures, those operations may have corresponding counterpartmeans-plus-function components with similar numbering.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein, but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communications by a userequipment (UE), comprising: selecting, from a plurality of transmissionpoints involved in uplink (UL) coordinated multipoint (CoMP) operationswith the UE, a transmission point to associate with for path loss (PL)compensation; and adjusting power of one or more transmissions based onpath loss measured based on the selected transmission point.
 2. Themethod of claim 1, wherein: the transmission points comprisetransmission points of different class types forming a heterogeneousnetwork; and the selecting is based, at least in part, on a relativedifference in path loss between a transmission point of a first powerclass type and a transmission point of a second power class type.
 3. Themethod of claim 2, wherein: the transmission point of the first powerclass type comprises a macro transmission point; and the selectingcomprises selecting a macro transmission point if a measured path lossfor the macro transmission point is below a threshold value.
 4. Themethod of claim 3, wherein: the transmission point of the second powerclass type comprises a pico transmission point; and the threshold valueis determined based, at least in part, on a path loss of the picotransmission point and a bias amount.
 5. A method for controllingtransmission power of one or more user equipments (UEs) by a basestation, comprising: utilizing a first power control algorithm to adjusttransmit power of a first contention-based random access channel (RACH);and utilizing a second power control algorithm to adjust transmit powerof a non contention-based RACH.
 6. The method of claim 5, wherein thefirst power control algorithm increases transmit power for transmissionof a contention-based RACH faster than the second power controlalgorithm increases transmit power for transmission ofnon-contention-based RACH.
 7. The method of claim 5, wherein: the firstpower control algorithm utilizes transmit power control (TPC) commandswith a first step size; and the second power control algorithm utilizesTPC commands with a second step size that is larger than the first stepsize.
 8. The method of claim 7, wherein the TPC commands of the secondstep size are signaled in an enhanced physical downlink control channel(PDCCH) that utilizes resources in a data region of a downlink subframe.9. A method for wireless communications by a user equipment (UE),comprising: utilizing a first power control algorithm to adjust transmitpower of a first contention-based random access channel (RACH); andutilizing a second power control algorithm to adjust transmit power of anon contention-based RACH.
 10. The method of claim 9, wherein the firstpower control algorithm increases transmit power for transmission of acontention-based RACH faster than the second power control algorithmincreases transmit power for transmission of non-contention-based RACH.11. The method of claim 9, wherein: the first power control algorithmutilizes transmit power control (TPC) commands with a first step size;and the second power control algorithm utilizes TPC commands with asecond step size that is larger than the first step size.
 12. The methodof claim 11, wherein the TPC commands of the second step size aresignaled in an enhanced physical downlink control channel (PDCCH) thatutilizes resources in a data region of a downlink subframe.
 13. A methodfor controlling transmission power of one or more user equipments (UEs)by a base station, comprising: determining mobility of a UE; andselecting a power control algorithm for use in controlling power oftransmissions from the UE, based on the determined mobility.
 14. Themethod of claim 13, wherein the selecting comprises: disabling open loop(OL) power control in response to determining high mobility.
 15. Themethod of claim 13, wherein the selecting comprises: utilizing open loop(OL) power control in response to determining low mobility and if one ormore UL transmission point for the UE are the same as DL transmissionpoints for the UE.
 16. The method of claim 13, wherein the selectingcomprises: utilizing closed loop (CL) power control in response todetermining low mobility and if one or more UL transmission point forthe UE are not the same as DL transmission points for the UE.
 17. Themethod of claim 13, wherein the selecting comprises: utilizing bothclosed loop (CL) and open loop (OL) power control in response todetermining low mobility and if the one or more UL transmission pointfor the UE are not the same as DL transmission points for the UE.
 18. Amethod for wireless communications by a user equipment (UE), comprising:measuring path loss (PL) for a plurality of transmission points involvedin uplink (UL) coordinate multipoint (CoMP) transmissions with the UE;and selecting, based on the PL measurements, one of the transmissionpoints for applying PL compensation.
 19. The method of claim 18, whereinthe selecting comprises: selecting a transmission point with a smallestpath loss for applying PL compensation.
 20. The method of claim 19,wherein the measuring comprises: measuring common reference signals(CRS) from a first cell by performing interference cancellation (IC) ofCRS from at least a second cell.
 21. The method of claim 19, furthercomprising: receiving signaling indicating a set of the transmissionpoints involved in the UL CoMP transmissions and corresponding powersettings for the set of transmission points.
 22. The method of claim 19,wherein the measuring comprises: measuring channel state informationreference signals (CSI-RS) transmitted from the set of transmissionpoints involved in UL CoMP operations.
 23. The method of claim 22,further comprising: receiving signaling indicating a list of CSI-RSports and corresponding power settings for the set of transmissionpoints.
 24. The method of claim 23, wherein the signaling indicatesdisjoint sets of CSI-RS ports specified for DL CoMP measurements and ULCoMP measurements.
 25. A method for wireless communications by a basestation, comprising: measuring path loss (PL) between a UE and one ormore transmission points involved in uplink (UL) coordinate multipoint(CoMP) transmissions with the UE; and taking action to compensate forthe measured path loss.
 26. The method of claim 25, wherein the actioncomprises: performing a power shaping algorithm.
 27. The method of claim26, wherein the power shaping algorithm comprises transmitting one ormore transmit power control (TPC) commands to adjust the UE transmitpower to achieve partial path loss compensation based rate shaping. 28.The method of claim 25, wherein the measuring comprises calculating PLbased on received signal power, a maximum transmit power of the UE, anda power headroom report of the UE.
 29. The method of claim 25, whereinthe action comprises: reducing interference to the UE caused by one ormore other UEs by controlling the one or more other UEs.
 30. A method ofwireless communications by a user equipment (UE), comprising: measuringboth common reference signals (CRS) and channel state informationreference signals (CSI-RS) transmitted from transmission points involvedin uplink (UL) CoMP transmissions; and performing power control for ULtransmissions based on both the CRS and the CSI-RS.
 31. The method ofclaim 30, wherein performing power control for UL transmissions based onboth the CRS and the CSI-RS comprises: measuring pathloss (PL) based onCRS; and determining whether to use open loop (OL) power control basedon CSI-RS.
 32. The method of claim 30, wherein performing power controlfor UL transmissions based on both the CRS and the CSI-RS comprises:measuring pathloss (PL) for multiple transmission points based on CRS;and determining which PL to use for power control based on CSI-RS. 33.The method of claim 30, further comprising: detecting one or more cellsbased on CSI-RS; and enabling CRS interference cancellation (CRS-IC)after detecting the one or more cells.
 34. The method of claim 30,wherein performing power control for UL transmissions based on both theCRS and the CSI-RS comprises: measuring a base path loss (PL) based onCRS; and measuring a difference in path loss (PL) based on CSI-RS. 35.An apparatus for wireless communications by a user equipment (UE),comprising: means for selecting, from a plurality of transmission pointsinvolved in uplink (UL) coordinated multipoint (CoMP) operations withthe UE, a transmission point to associate with for path loss (PL)compensation; and means for adjusting power of one or more transmissionsbased on path loss measured based on the selected transmission point.36. An apparatus for controlling transmission power of one or more userequipments (UEs) by a base station, comprising: means for utilizing afirst power control algorithm to adjust transmit power of a firstcontention-based random access channel (RACH) from a user equipment(UE); and means for utilizing a second power control algorithm to adjusttransmit power of a non contention-based RACH from a UE.
 37. Anapparatus for wireless communications by a user equipment (UE),comprising: means for utilizing a first power control algorithm toadjust transmit power of a first contention-based random access channel(RACH) to a base station; and means for utilizing a second power controlalgorithm to adjust transmit power of a non contention-based RACH to abase station.
 38. An apparatus for controlling transmission power of oneor more user equipments (UEs) by a base station, comprising: means fordetermining mobility of a UE; and means for selecting a power controlalgorithm for use in controlling power of transmissions from the UE,based on the determined mobility.
 39. An apparatus for wirelesscommunications by a user equipment (UE), comprising: means for measuringpath loss (PL) for a plurality of transmission points involved in uplink(UL) coordinate multipoint (CoMP) transmissions with the UE; and meansfor selecting, based on the PL measurements, one of the transmissionpoints for applying PL compensation.
 40. An apparatus for wirelesscommunications by a base station, comprising: means for measuring pathloss (PL) between a UE and one or more transmission points involved inuplink (UL) coordinate multipoint (CoMP) transmissions with the UE; andmeans for taking action to compensate for the measured path loss.
 41. Anapparatus for wireless communications by a user equipment (UE),comprising: means for measuring both common reference signals (CRS) andchannel state information reference signals (CSI-RS) transmitted fromtransmission points involved in uplink (UL) CoMP transmissions; andmeans for performing power control for UL transmissions based on boththe CRS and the CSI-RS.
 42. An apparatus for wireless communications bya user equipment (UE), comprising: at least one processor configured toselect, from a plurality of transmission points involved in uplink (UL)coordinated multipoint (CoMP) operations with a UE, a transmission pointto associate with for path loss (PL) compensation and adjust power ofone or more transmissions based on path loss measured based on theselected transmission point; and a memory coupled with the at least oneprocessor.
 43. An apparatus for wireless communications for controllingtransmission power of one or more user equipments (UEs) by a basestation, comprising: at least one processor configured to utilize afirst power control algorithm to adjust transmit power of a firstcontention-based random access channel (RACH) from a UE and utilize asecond power control algorithm to adjust transmit power of a noncontention-based RACH from a UE; and a memory coupled with the at leastone processor.
 44. An apparatus for wireless communications by a userequipment (UE), comprising: at least one processor configured to utilizea first power control algorithm to adjust transmit power of a firstcontention-based random access channel (RACH) to a base station andutilizing a second power control algorithm to adjust transmit power of anon contention-based RACH to a base station; and a memory coupled withthe at least one processor.
 45. An apparatus for wireless communicationsfor controlling transmission power of one or more user equipments (UEs)by a base station, comprising: at least one processor configured todetermine mobility of a UE and select a power control algorithm for usein controlling power of transmissions from the UE, based on thedetermined mobility; and a memory coupled with the at least oneprocessor.
 46. An apparatus for wireless communications by a userequipment (UE), comprising: at least one processor configured to measurepath loss (PL) for a plurality of transmission points involved in uplink(UL) coordinate multipoint (CoMP) transmissions with the UE and select,based on the PL measurements, one of the transmission points forapplying PL compensation; and a memory coupled with the at least oneprocessor.
 47. An apparatus for wireless communications by a basestation, comprising: at least one processor configured to measure pathloss (PL) between a user equipment (UE) and one or more transmissionpoints involved in uplink (UL) coordinate multipoint (CoMP)transmissions with the UE and take action to compensate for the measuredpath loss; and a memory coupled with the at least one processor.
 48. Anapparatus for wireless communications by a user equipment (UE),comprising: at least one processor configured to measure both commonreference signals (CRS) and channel state information reference signals(CSI-RS) transmitted from transmission points involved in uplink (UL)CoMP transmissions perform power control for UL transmissions based onboth the CRS and the CSI-RS; and a memory coupled with the at least oneprocessor.
 49. A program product comprising a computer readable mediumhaving instructions stored thereon, the instructions generallyexecutable by one or more processors for wireless communications by auser equipment (UE), the instructions comprising: selecting, from aplurality of transmission points involved in uplink (UL) coordinatedmultipoint (CoMP) operations with a UE, a transmission point toassociate with for path loss (PL) compensation; and adjusting power ofone or more transmissions based on path loss measured based on theselected transmission point.
 50. The program product of claim 49,wherein: the transmission points comprise transmission points ofdifferent class types forming a heterogeneous network; and the selectingis based, at least in part, on a relative difference in path lossbetween a transmission point of a first power class type and atransmission point of a second power class type.
 51. The program productof claim 50, wherein: the transmission point of the first power classtype comprises a macro transmission point; and the selecting comprisesselecting a macro transmission point if a measured path loss for themacro transmission point is below a threshold value.
 52. The method ofclaim 51, wherein: the transmission point of the second power class typecomprises a pico transmission point; and the threshold value isdetermined based, at least in part, on a path loss of the picotransmission point and a bias amount.
 53. A program product comprising acomputer readable medium having instructions stored thereon, theinstructions generally executable by one or more processors forcontrolling transmission power of one or more user equipments (UEs) by astation, the instructions comprising: utilizing a first power controlalgorithm to adjust transmit power of a first contention-based randomaccess channel (RACH); and utilizing a second power control algorithm toadjust transmit power of a non contention-based RACH.
 54. The programproduct of claim 53, wherein the first power control algorithm increasestransmit power for transmission of a contention-based RACH faster thanthe second power control algorithm increases transmit power fortransmission of non-contention-based RACH.
 55. The program product ofclaim 53, wherein: the first power control algorithm utilizes transmitpower control (TPC) commands with a first step size; and the secondpower control algorithm utilizes TPC commands with a second step sizethat is larger than the first step size.
 56. The program product ofclaim 55, wherein the TPC commands of the second step size are signaledin an enhanced physical downlink control channel (PDCCH) that utilizesresources in a data region of a downlink subframe.
 57. A program productcomprising a computer readable medium having instructions storedthereon, the instructions generally executable by one or more processorsfor wireless communications by a user equipment (UE), the instructionscomprising: utilizing a first power control algorithm to adjust transmitpower of a first contention-based random access channel (RACH); andutilizing a second power control algorithm to adjust transmit power of anon contention-based RACH.
 58. The program product of claim 57, whereinthe first power control algorithm increases transmit power fortransmission of a contention-based RACH faster than the second powercontrol algorithm increases transmit power for transmission ofnon-contention-based RACH.
 59. The program product of claim 57, wherein:the first power control algorithm utilizes transmit power control (TPC)commands with a first step size; and the second power control algorithmutilizes TPC commands with a second step size that is larger than thefirst step size.
 60. The program product of claim 59, wherein the TPCcommands of the second step size are signaled in an enhanced physicaldownlink control channel (PDCCH) that utilizes resources in a dataregion of a downlink subframe.
 61. A program product comprising acomputer readable medium having instructions stored thereon, theinstructions generally executable by one or more processors forcontrolling transmission power of one or more user equipments (UEs) by astation, the instructions comprising: determining mobility of a UE; andselecting a power control algorithm for use in controlling power oftransmissions from the UE, based on the determined mobility.
 62. Theprogram product of claim 61, wherein the selecting comprises: disablingopen loop (OL) power control in response to determining high mobility.63. The program product of claim 61, wherein the selecting comprises:utilizing open loop (OL) power control in response to determining lowmobility and if one or more UL transmission point for the UE are thesame as DL transmission points for the UE.
 64. The program product ofclaim 61, wherein the selecting comprises: utilizing closed loop (CL)power control in response to determining low mobility and if one or moreUL transmission point for the UE are not the same as DL transmissionpoints for the UE.
 65. The program product of claim 61, wherein theselecting comprises: utilizing both closed loop (CL) and open loop (OL)power control in response to determining low mobility and if the one ormore UL transmission point for the UE are not the same as DLtransmission points for the UE.
 66. A program product comprising acomputer readable medium having instructions stored thereon, theinstructions generally executable by one or more processors for wirelesscommunications by a user equipment (UE), the instructions comprising:measuring path loss (PL) for a plurality of transmission points involvedin uplink (UL) coordinate multipoint (CoMP) transmissions with the UE;and selecting, based on the PL measurements, one of the transmissionpoints for applying PL compensation.
 67. The program product of claim66, wherein the selecting comprises: selecting a transmission point witha smallest path loss for applying PL compensation.
 68. The programproduct of claim 67, wherein the measuring comprises: measuring commonreference signals (CRS) from a first cell by performing interferencecancellation (IC) of CRS from at least a second cell.
 69. The programproduct of claim 67, the instructions further comprising: receivingsignaling indicating a set of the transmission points involved in the ULCoMP transmissions and corresponding power settings for the set oftransmission points.
 70. The program product of claim 67, wherein themeasuring comprises: measuring channel state information referencesignals (CSI-RS) transmitted from the set of transmission pointsinvolved in UL CoMP operations.
 71. The program product of claim 70, theinstructions further comprising: receiving signaling indicating a listof CSI-RS ports and corresponding power settings for the set oftransmission points.
 72. The program product of claim 71, wherein thesignaling indicates disjoint sets of CSI-RS ports specified for DL CoMPmeasurements and UL CoMP measurements.
 73. A program product comprisinga computer readable medium having instructions stored thereon, theinstructions generally executable by one or more processors for wirelesscommunications by a base station, the instructions comprising: measuringpath loss (PL) between a user equipment (UE) and one or moretransmission points involved in uplink (UL) coordinate multipoint (CoMP)transmissions with the UE; and taking action to compensate for themeasured path loss.
 74. The program product of claim 73, wherein theaction comprises: performing a power shaping algorithm.
 75. The programproduct of claim 74, wherein the power shaping algorithm comprisestransmitting one or more transmit power control (TPC) commands to adjustthe UE transmit power to achieve partial path loss compensation basedrate shaping.
 76. The program product of claim 73, wherein the measuringcomprises calculating PL based on received signal power, a maximumtransmit power of the UE, and a power headroom report of the UE.
 77. Theprogram product of claim 73, wherein the action comprises: reducinginterference to the UE caused by one or more other UEs by controllingthe one or more other UEs.
 78. A program product comprising a computerreadable medium having instructions stored thereon, the instructionsgenerally executable by one or more processors for wirelesscommunications by a user equipment (UE), the instructions comprising:measuring both common reference signals (CRS) and channel stateinformation reference signals (CSI-RS) transmitted from transmissionpoints involved in uplink (UL) CoMP transmissions; and performing powercontrol for UL transmissions based on both the CRS and the CSI-RS. 79.The program product of claim 78, wherein performing power control for ULtransmissions based on both the CRS and the CSI-RS comprises: measuringpathloss (PL) based on CRS; and determining whether to use open loop(OL) power control based on CSI-RS.
 80. The program product of claim 78,wherein performing power control for UL transmissions based on both theCRS and the CSI-RS comprises: measuring pathloss (PL) for multipletransmission points based on CRS; and determining which PL to use forpower control based on CSI-RS.
 81. The program product of claim 78, theinstructions further comprising: detecting one or more cells based onCSI-RS; and enabling CRS interference cancellation (CRS-IC) afterdetecting the one or more cells.
 82. The program product of claim 78,wherein performing power control for UL transmissions based on both theCRS and the CSI-RS comprises: measuring a base path loss (PL) based onCRS; and measuring a difference in path loss (PL) based on CSI-RS.